A fuel cell is configured by laminating a reaction layer on a solid electrolyte film and the characteristics of the reaction layer on an air electrode side that is a fuel cell reaction field largely influence performance of the fuel cell.
The inventor of the present invention has disclosed, as such an air electrode side reaction layer, a reaction film having a PFF structure (registered trade mark: the same applies hereinafter) (Patent Document 1). Here, the PFF structure refers to a structure in which a hydrophilic functional group in a side chain of a polymer electrolyte is aligned on a catalyst side to form a hydrophilic region on the catalyst. Here, the catalyst is formed by supporting catalyst metal particles on a carrier containing carbon particles or the like.
See Patent Document 2 and Non-patent Document 1 as a document disclosing a technology related to the present invention.